The protection of information recorded on magnetic recording media from unauthorized duplication and use has been a recent subject of considerable interest. This interest has assumed even greater proportions with the proliferation of "personal computers". The success of the "personal computer" is due in large part to the wide assortment of software systems which are available for use therewith. A variety of games, accounting programs, sophisticated scientific programs, graphics programs, data management programs and the like and presently available for purchase by the "personal computer" user. Although such software is usually protected under the copyright laws of the United States, the temptation to duplicate a copy of the software for a friend, or to rent a copy for unauthorized duplication , is often too great to resist. Accordingly, the unlawful duplication and use of copyrighted software has become a major problem.
There are known various methods for the prevention of duplication of magnetically recorded signals, software and/or data bases. One such method involves altering the format of the software stored on a disk or tape in such a manner as to confuse standard computer operating system based copying routines, thereby rendering the stored software uncopyable. This method of protection, however, can be easily defeated through the use of format independent copying routines.
Other methods of protection involve the attachment of specialized electronic devices to the computer system's hardware. Such devices, however, unnecessarily limit the use of the computer hardware and require user cooperation to be effective. The employment of an additional piece of hardware also makes such methods expensive.
Accordingly, the protection systems which have been known heretofore have not been completely satisfactory.